Campaigners have warned that growing numbers of youngsters are hooked on graphic films found online.

A debate is raging in Whitehall about whether internet service providers should be forced to make it easier for parents to block online porn from new computers.

Education Liz Truss raised the prospect of porn-related lessons as part of ‘age appropriate’ studies in a reply in the House of Commons.

She told MPs: “The Government wants all young people to have high quality, age appropriate sex and relationships education.

“The current non-statutory programmes of study for Personal, Social, Health and Economic education, which include sex and relationship education, can provide opportunities for schools to teach about pornography.

“We believe that teachers should be free to use their professional judgement to decide what to include in PSHE lessons, according to needs of their pupils.”

Teaching unions have called for students to be taught about porn from the age of 10. A study last month suggested children as young as 11 were becoming addicted to internet pornography giving them “unrealistic expectations” of sex.

In June 2012 a 14-year-old boy who raped a nine-year-old girl after watching hard-core pornography online was spared jail. His lawyer said the boy, who was just 12 at the time of the attack, wanted to feel grown up.

Last night a Department for Education said the minister was not encouraging teachers to allow children to watch pornography in schools.

She said: “Obviously the Minister was saying that PSHE could give schools a chance to teach children about the dangers of pornography – something which is a growing problem in our schools that parents are rightly very concerned about.”